Richtext, Word formatting, Copy & Paste

Hello formidable team,
we use the WordPress plugin on the following page: http://www.batterieforum-deutschland.de/kongress/posteranmeldung/
There is the field "Abstract". Almost at the bottom. There we have a text field of the type Richtext.
Some background informations: the users should insert a text, which theire usually wrote in Word. Most users make copy and paste here. The special: In the text field, all formatting should disappear (like the striphtml). For this reason, you should actually use the format text paragraph and not how we use Richtext. The second challenge is to have high and low characters
. Since this is a matter of scientific and mathematical content.
Now we have decided to use a richtext, and the editable toolbar will be dimmed. Disadvantage: all formatting from Word is accepted. And it does not work in all browsers. Do you have an idea how we can make a simple textarea from this, but still allow high and low characters
and not all Word formatting are taken?